JP2020043282A - Storage device - Google Patents

Abstract

To provide a high-quality storage device.SOLUTION: The storage device includes a variable resistance element 22. The variable resistance element 22 includes a stacked body 120, the stacked body including a ferromagnetic body 210, a ferromagnetic body 230, and a nonmagnetic body 220 provided between the ferromagnetic body 210 and the ferromagnetic body 230 and containing a boron-added rare earth oxide. If a structure containing the two ferromagnets is used as a storage layer, reversal of magnetization directions of the two ferromagnetic bodies can be efficiently performed by using an STT between the two ferromagnetic bodies, and a write current of the storage layer can be reduced.SELECTED DRAWING: Figure 3

Description

  Embodiments relate to a storage device.

  A storage device having a magnetic element is known.

US Patent Application Publication No. 2017/0263858

  Provide a high-quality storage device.

  The storage device according to the embodiment includes a resistance change element, wherein the resistance change element is provided between a first ferromagnetic material, a second ferromagnetic material, and the first ferromagnetic material and the second ferromagnetic material. And a first non-magnetic material including a boron-added rare earth oxide.

FIG. 2 is a block diagram illustrating an example of a configuration of a storage device according to the first embodiment. FIG. 3 is a cross-sectional view illustrating an example of a configuration of a memory cell of the storage device according to the first embodiment. FIG. 4 is a cross-sectional view illustrating an example of the configuration of the variable resistance element of the storage device according to the first embodiment. FIG. 4 is a cross-sectional view of an exemplary laminate including an example of the laminate illustrated in FIG. 3 and a cross-sectional view of an exemplary laminate including a configuration similar to the laminate illustrated in FIG. 3. FIG. 4B is a diagram showing an example of a graph in which the value of the amount of magnetization measured when an external magnetic field is applied to each of the laminates shown in FIG. 4A is plotted. FIG. 4 is a schematic diagram illustrating an example of a write operation of setting the resistance change element to a high resistance state in the storage device according to the first embodiment. FIG. 4 is a schematic diagram showing an example of a write operation for setting a variable resistance element to a low resistance state in the storage device according to the first embodiment. FIG. 3 is a cross-sectional view of an exemplary laminate as a comparative example of the first embodiment. FIG. 7B is a view showing an example of a graph in which the value of the amount of magnetization measured when an external magnetic field is applied to the laminate shown in FIG. 7A.

  Hereinafter, embodiments will be described with reference to the drawings. In the following description, components having the same functions and configurations are denoted by the same reference numerals. When a plurality of components having a common reference numeral are distinguished, the common reference numeral is distinguished by adding a suffix. In the case where it is not particularly necessary to distinguish a plurality of constituent elements, the plurality of constituent elements are given only common reference numerals, and no suffix is added.

<First embodiment>
The storage device according to the first embodiment will be described. The storage device according to the first embodiment employs, for example, a perpendicular magnetization method using, as a storage element, a resistance change element utilizing a tunneling magnetoresistance (TMR) effect by a magnetic tunnel junction (MTJ: Magnetic Tunnel Junction). It includes a magnetic storage device (MRAM: Magnetoresistive Random Access Memory). Note that the TMR effect is a phenomenon in which the magnetization direction of a ferromagnetic material is changed by applying a magnetic field, thereby changing the electric resistance when a tunnel current flows. In the following description, the above-described magnetic storage device will be described as an example of the storage device.

[Configuration example]
(1) Configuration of Storage Device First, the configuration of the storage device according to the first embodiment will be described.
FIG. 1 is a block diagram illustrating an example of a configuration of the storage device 1 according to the first embodiment. As shown in FIG. 1, the storage device 1 includes a memory cell array 11, a current sink 12, a sense amplifier and a write driver (SA / WD) 13, a row decoder 14, a page buffer 15, an input / output circuit 16, and a control unit 17. Including.

  The memory cell array 11 includes a plurality of memory cells MC associated with a row (row) and a column (column). For example, the memory cells MC associated with the same row are connected to the same word line WL. For example, a first end of the memory cell MC associated with the same column is connected to the same bit line BL, and a second end of the memory cell MC associated with the same column is connected to the same source line / BL. Connected.

  Current sink 12 is connected to bit line BL and source line / BL. The current sink 12 sets the bit line BL or the source line / BL to the ground potential in operations such as data writing and reading.

  SA / WD 13 includes a write driver WD and a sense amplifier SA. For example, each of the write drivers WD is connected to the associated bit line BL and source line / BL. For example, each of the sense amplifiers SA is connected to an associated bit line BL. Each of the write drivers WD supplies a current to the target memory cell MC via the bit line BL and the source line / BL associated with each other, and writes data to the memory cell MC. Further, each of the sense amplifiers SA supplies a current to the target memory cell MC via the bit line BL associated with the sense amplifier SA, and reads data from the memory cell MC.

  Row decoder 14 is connected to memory cell array 11 via word line WL. The row decoder 14 decodes a row address designating the word line WL to which the memory cell array 11 is connected. After that, the row decoder 14 selects a word line WL specified by the decoded row address, and applies a voltage that enables operations such as data writing and reading to the selected word line WL.

  The page buffer 15 temporarily holds data to be written in the memory cell array 11 and data read from the memory cell array 11 in data units called pages.

  The input / output circuit 16 transmits various signals received from the outside of the storage device 1 to the control unit 17 and the page buffer 15, and transmits various information from the control unit 17 and the page buffer 15 to the outside of the storage device 1.

  The control unit 17 is connected to the current sink 12, the SA / WD 13, the row decoder 14, the page buffer 15, and the input / output circuit 16. The control unit 17 controls the current sink 12, the SA / WD 13, the row decoder 14, and the page buffer 15 in accordance with various signals received by the input / output circuit 16 from outside the storage device 1.

(2) Configuration of Memory Cell Next, the configuration of the memory cell of the storage device according to the first embodiment will be described.
FIG. 2 is a cross-sectional view illustrating an example of a configuration of the memory cell MC of the storage device 1 according to the first embodiment. In the following description, a plane parallel to the semiconductor substrate 20 is defined as an xy plane, and, for example, an axis perpendicular to the xy plane is defined as a z-axis. The x-axis and the y-axis are defined as, for example, axes that are orthogonal to each other in the xy plane. The cross-sectional view shown in FIG. 2 corresponds to a cross section of the memory cell MC cut along the xz plane. In the following description, the direction toward the positive direction of the z-axis will be described as upward, and the direction toward the negative direction of the z-axis will be described below.

  As shown in FIG. 2, the memory cell MC is provided on a semiconductor substrate 20, and includes a selection transistor 21 and a variable resistance element 22. The selection transistor 21 is provided as a switch that controls supply and stop of current when writing and reading data to and from the variable resistance element 22. The resistance change element 22 includes, for example, a plurality of stacked substances. The resistance value of the resistance change element 22 can be switched between a low resistance state and a high resistance state by a current flowing in a direction penetrating the layer interface, for example, a direction perpendicular to the layer interface. Data can be written to the variable resistance element 22 by utilizing the change in the resistance state, and the variable resistance element 22 functions as a storage element that holds the written data in a nonvolatile manner and can read the data. I do.

  The selection transistor 21 includes a gate connected to a wiring layer 23 functioning as a word line WL, and a pair of source or drain regions 24 provided on the surface of the semiconductor substrate 20 at both ends of the gate in the x direction. Including. The selection transistor 21 is formed in an active region of the semiconductor substrate 20. The active regions are insulated from each other by, for example, an element isolation region (STI: Shallow Trench Isolation) (not shown) so as not to be electrically connected to the active region of another memory cell MC.

  The wiring layer 23 is provided along the y direction via the insulating layer 25 on the semiconductor substrate 20. For example, the gate of the select transistor 21 (not shown) of another memory cell MC arranged in the y direction is provided. Connected in common. The wiring layers 23 are arranged, for example, in the x direction.

  A contact plug 26 is provided on one of the source region or the drain region 24 of the selection transistor 21. The resistance change element 22 is provided on the upper surface of the contact plug 26. A contact plug 27 is provided on the upper surface of the resistance change element 22. The upper surface of the contact plug 27 is connected to the wiring layer 28. The wiring layer 28 functions as the bit line BL, is provided along the x direction, and is commonly connected to, for example, the resistance change element 22 (not shown) of another memory cell MC arranged in the x direction.

  A contact plug 29 is provided on the other source region or drain region 24 of the select transistor 21. The upper surface of contact plug 29 is connected to wiring layer 30. The wiring layer 30 functions as the source line / BL, is provided along the x direction, and is commonly connected to, for example, the selection transistors 21 (not shown) of other memory cells MC arranged in the x direction.

  The wiring layers 28 and 30 are arranged, for example, in the y direction. The wiring layer 28 is located, for example, above the wiring layer 30. The select transistor 21, the resistance change element 22, the wiring layers 23, 28, and 30, and the contact plugs 26, 27, and 29 are covered with an interlayer insulating film 31.

  The other variable resistance elements 22 (not shown) arranged along the x direction or the y direction with respect to the variable resistance element 22 are provided, for example, on the same layer. That is, in the memory cell array 11, the plurality of resistance change elements 22 are arranged, for example, along the direction in which the semiconductor substrate 20 spreads.

(3) Configuration of Variable Resistance Element Next, the configuration of the variable resistance element of the storage device according to the first embodiment will be described.
FIG. 3 is a cross-sectional view illustrating an example of the configuration of the resistance change element 22 of the storage device 1 according to the first embodiment. The cross-sectional view illustrated in FIG. 3 corresponds to a cross section of the variable resistance element 22 cut along the xz plane described above.

  As shown in FIG. 3, the resistance change element 22 includes a nonmagnetic body 110, a stacked body 120, a nonmagnetic body 130, and a ferromagnetic body 140. The non-magnetic material 110, the laminated body 120, the non-magnetic material 130, and the ferromagnetic material 140 are z z from the semiconductor substrate 20 side in the order of the non-magnetic material 110, the laminated body 120, the non-magnetic material 130, and the ferromagnetic material 140. Laminated in the axial direction.

  The non-magnetic material 110 functions as, for example, an underlayer. The non-magnetic material 130 functions as, for example, a tunnel barrier layer. That is, the stacked body 120, the non-magnetic body 130, and the ferromagnetic body 140 form a magnetic tunnel junction. The ferromagnetic material 140 has a fixed magnetization in a certain direction, and functions as, for example, a reference layer.

  The stacked body 120 has a variable magnetization along a certain direction in a steady state, and functions as, for example, a storage layer. The steady state refers to a state in which no voltage is applied and the magnetic field is not positioned in the magnetic field, and the transition of the magnetization state is completed and stable.

  A set of the stacked body 120, the non-magnetic body 130, and the ferromagnetic body 140 exhibits the TMR effect. The TMR effect indicates that in a structure including two ferromagnetic materials sandwiching an insulator, when the magnetization directions of the two ferromagnetic materials are parallel, the structure shows the minimum resistance value and the magnetization of the two ferromagnetic materials When the directions are antiparallel, this indicates a phenomenon in which the structure shows the maximum resistance value. The resistance change element 22 can take one of a low resistance state and a high resistance state depending on whether the magnetization direction of the stacked body 120 is parallel or antiparallel to the magnetization direction of the ferromagnetic body 140.

  When the magnetization direction of the ferromagnetic body 140 and the magnetization direction of the stacked body 120 are parallel, the resistance value of the resistance change element 22 is the lowest. That is, the resistance change element 22 is set to the low resistance state. This low resistance state is called a “P (Parallel) state” and is defined as, for example, a state of data “0”.

  When the magnetization direction of the ferromagnetic material 140 and the magnetization direction of the stacked body 120 are antiparallel, the resistance value of the resistance change element 22 is the highest. That is, the resistance change element 22 is set to the high resistance state. This high resistance state is called an “AP (Anti-Parallel) state” and is defined as, for example, a state of data “1”.

  The stacked body 120 includes a ferromagnetic body 210, a non-magnetic body 220, and a ferromagnetic body 230. The ferromagnetic material 210, the non-magnetic material 220, and the ferromagnetic material 230 are stacked in the z-axis direction from the semiconductor substrate 20 side in the order of the ferromagnetic material 210, the non-magnetic material 220, and the ferromagnetic material 230. The ferromagnetic body 210 functions, for example, as a first storage layer. The ferromagnetic material 230 functions, for example, as a second storage layer. The nonmagnetic material 220 functions as, for example, a function layer, and functions as a tunnel barrier layer. That is, the ferromagnetic material 210, the non-magnetic material 220, and the ferromagnetic material 230 form a magnetic tunnel junction, and can exhibit the TMR effect.

  The magnetization of the ferromagnetic material 210 and the magnetization of the ferromagnetic material 230 are in the same direction in a steady state. Therefore, the magnetization direction of the stacked body 120 is the magnetization direction of the ferromagnetic bodies 210 and 230 in a steady state.

  Thus, the structure functioning as the storage layer is realized by the two ferromagnetic materials 210 and 230. The non-magnetic body 220 is provided between the ferromagnetic bodies 210 and 230 and includes an oxide. By providing an oxide between the ferromagnetic materials 210 and 230 in this manner, interface anisotropy is generated that directs the magnetization of the ferromagnetic materials 210 and 230 in a direction perpendicular to the interface between the layers. Therefore, the perpendicular magnetization of the stacked body 120 has higher resistance to thermal disturbance than when the storage layer is formed of one ferromagnetic material. Also, the two ferromagnetic materials having perpendicular magnetization are stabilized in parallel with each other in order to minimize magnetostatic energy.

  The variable resistance element 22 shown in FIG. 3 is merely an example, and the variable resistance element 22 may include additional layers other than those described above.

Next, the nonmagnetic material 110, the laminated body 120, the nonmagnetic material 130, and the ferromagnetic material 140 will be further described.
The non-magnetic material 110 has conductivity and includes a non-magnetic material. For example, the non-magnetic material 110 is made of an oxide containing a metal element such as the following alkali metal, alkaline earth metal, and rare earth metal, for example, magnesium oxide (MgO), rare earth oxide (YO, LaO, EuO, GdO). Alternatively, nitrides containing metal elements such as the following alkali metals, base metals and transition metals, for example, magnesium nitride (MgN), zirconium nitride (ZrN), niobium nitride (NbN), aluminum nitride (AlN), hafnium nitride ( HfN), tantalum nitride (TaN), tungsten nitride (WN), chromium nitride (CrN), molybdenum nitride (MoN), titanium nitride (TiN), and vanadium nitride (VN), or a boride containing a 5d transition metal; For example, it contains at least one of compounds such as HfB and TaB. Further, the nonmagnetic material 110 may include a mixture of the above-described oxide, nitride, or boride. That is, the nonmagnetic material 110 may include not only a binary compound composed of two kinds of elements but also a ternary compound composed of three kinds of elements, for example, boride oxide (GdBO) or the like.

  The nonmagnetic material 130 has, for example, an insulating property and includes a nonmagnetic material. For example, the non-magnetic body 130 includes magnesium oxide (MgO).

  The ferromagnetic material 140 includes a ferromagnetic material having conductivity and having a direction perpendicular to the interface between the ferromagnetic material 140 and another layer, for example, an easy axis along the z-axis. For example, the ferromagnetic material 140 includes iron cobalt boron (FeCoB) as a ferromagnetic material having perpendicular magnetization. The resistance change element 22 has, as a further ferromagnetic material, perpendicular magnetization in which magnetization is coupled antiparallel to the ferromagnetic material 140 on the opposite side of the ferromagnetic material 140 from the nonmagnetic material 130. At least one of cobalt platinum (CoPt), cobalt nickel (CoNi), and cobalt palladium (CoPd) may be included. The magnitude of the magnetization of the further ferromagnetic material is larger than the magnitude of the magnetization of the ferromagnetic material 140. Ruthenium (Ru) and iridium (Ir) are used, for example, to couple the two ferromagnetic materials antiparallel. The magnetization direction of the ferromagnetic body 140 is fixed, and faces either the laminate 120 side or the opposite side thereof (in the example of FIG. 3, it faces the opposite side to the laminate 120 side). “The magnetization direction is fixed” means that the magnetization direction does not change depending on a magnetic field, a current, or the like having a magnitude that reverses the magnetization direction of the stacked body 120 used in the present embodiment. On the other hand, “the magnetization direction is variable” means that the magnetization direction can be changed by the magnetic field, the current, or the like. The reversal of the magnetization direction of the stacked body 120 means that the magnetization direction of each of the ferromagnetic bodies 210 and 230 included in the stacked body 120 is directed to one of the semiconductor substrate 20 side and the ferromagnetic body 140 side. Means to reverse the object in the other direction.

  Each of the ferromagnetic materials 210 and 230 has conductivity and includes a ferromagnetic material. For example, ferromagnetic materials 210 and 230 each include iron cobalt boron (FeCoB) or iron boride (FeB).

  For example, the perpendicular magnetic anisotropic magnetic field (Hk) of the ferromagnetic material 210 is larger than the perpendicular magnetic anisotropic magnetic field of the ferromagnetic material 230. And / or, the resonance magnetic field (Hr) of the magnetization of the ferromagnetic material 210 is larger than the resonance magnetic field of the magnetization of the ferromagnetic material 230. And / or the damping constant (α) of the magnetization of the ferromagnetic material 210 is larger than the damping constant of the magnetization of the ferromagnetic material 230. To that end, for example, the ferromagnetic material 210 can have a higher boron content than the ferromagnetic material 230. And / or the ferromagnetic material 210 can have a smaller thickness than the ferromagnetic material 230. In addition to providing the magnitude relation between the perpendicular magnetic anisotropic magnetic field resonance frequency and / or the damping constant of the ferromagnetic materials 210 and 230, the ferromagnetic materials 210 and 230 have the following configuration. Is also good. For example, the magnetization amount (Mst) of the ferromagnetic material 210 is smaller than the magnetization amount of the ferromagnetic material 230. The amount of magnetization is given by the product of the saturation magnetization (Ms) of the ferromagnetic material and the film thickness. To that end, for example, the ferromagnetic material 210 can have a lower saturation magnetization than the ferromagnetic material 230. And / or the ferromagnetic material 210 can have a smaller thickness than the ferromagnetic material 230. In order to adjust the resonance frequency, damping constant, and Ms of the ferromagnetic material 210, a transition metal such as Hf, Ta, W, Re, Ir, Pt, or the like is used for iron cobalt boron (FeCoB) or iron boride (FeB). Au, Zr, Nb, Mo, Ru, Rh, Pd, Ag, Ti, V, Cr, Mn, Ni, and Cu may be contained.

  The nonmagnetic material 220 is, for example, a dielectric material, has insulating properties, and includes a rare-earth element (RE) oxide to which boron is added (contained). The non-magnetic material 220 functions as a tunnel barrier layer. Boron-added rare earth element oxides (hereinafter, also simply referred to as “boron-doped rare-earth oxide (RE-BO)”) are, for example, scandium (Sc), yttrium ( Y), lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium ( Dy), at least one oxide of holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu). When the nonmagnetic material 220 having the characteristics of such a material is sandwiched between two ferromagnetic materials, the perpendicular magnetic anisotropy (PMA: Perpendicular Magnetic Anisotropy) of the two ferromagnetic materials is used. ) Can be maintained. That is, the ferromagnetic materials 210 and 230 have an easy axis of magnetization in a direction penetrating the interface between the ferromagnetic materials 210 and 230 and another layer, for example, an easy axis along the z-axis. Therefore, the magnetization directions of the ferromagnetic materials 210 and 230 and the ferromagnetic material 140 are perpendicular to the interface between the layers.

  The magnetization direction of each of the ferromagnetic materials 210 and 230 can be switched along the easy axis of magnetization, and data can be written to the resistance change element 22 by switching the magnetization direction of each of the ferromagnetic materials 210 and 230. . For that purpose, a spin injection writing method can be applied to the storage device 1. In the spin injection writing method, a writing current is directly supplied to the resistance change element 22, and the magnetization direction of the stacked body 120 is controlled by the writing current. That is, a spin transfer torque (STT) effect generated by the write current is used.

  When a write current is applied to the resistance change element 22 in the direction of arrow a1 shown in FIG. 3, that is, in the direction from the ferromagnetic body 140 to the stacked body 120, the magnetization direction of the stacked body 120 with respect to the magnetization direction of the ferromagnetic body 140 Become antiparallel.

  When a write current is applied to the resistance change element 22 in the direction of arrow a2 shown in FIG. 3, that is, in the direction from the stacked body 120 to the ferromagnetic body 140, the magnetization direction of the stacked body 120 with respect to the magnetization direction of the ferromagnetic body 140 Become parallel.

(4) Perpendicular Magnetic Anisotropy of Ferromagnetic Material as Storage Layer The fact that the laminated body 120 has perpendicular magnetic anisotropy as described above will be described.

  4A is a cross-sectional view of an exemplary stack including an example of the stack 120 illustrated in FIG. 3 and a cross-sectional view of an exemplary stack including a configuration similar to the stack 120 illustrated in FIG. is there. Although the structure of each laminate is specifically described, each layer described as being included in each laminate may include an arbitrary substance other than the substances explicitly described below.

  In the stacked body 22a shown in FIG. 4A, the magnesium oxide (MgO) layer 310a, the iron cobalt boron (FeCoB) layer 320a, the boron-added gadolinium oxide (GdBO) layer 330a, the iron cobalt boron (FeCoB) layer 340a, Each layer is stacked in the order of the magnesium oxide (MgO) layer 350a. Note that the layer 320a and the layer 340a have the same boron content and the same thickness.

  In the laminate 22b shown in FIG. 4B, the boron-added gadolinium oxide (GdBO) layer 310b, the iron-cobalt boron (FeCoB) layer 320b, the boron-added gadolinium oxide (GdBO) layer 330b, and the iron-cobalt boron (FeCoB) Each layer is laminated in the order of the layer 340b and the magnesium oxide (MgO) layer 350b. Note that the layer 320b and the layer 340b have the same boron content and the same thickness.

  In the stacked body 22c shown in FIG. 4C, a hafnium boron (HfB) layer 310c, an iron cobalt boron (FeCoB) layer 320c, a boron-added gadolinium oxide (GdBO) layer 330c, an iron cobalt boron (FeCoB) layer 340c, Each layer is laminated in the order of the magnesium oxide (MgO) layer 350c. Note that the layer 320c has a higher boron content and a smaller thickness than the layer 340c. Therefore, the perpendicular magnetic anisotropy magnetic field of the layer 320c is larger than that of the layer 340c.

  In the laminate 22d shown in (d) of FIG. 4A, a magnesium oxide (MgO) layer 310d, an iron cobalt boron (FeCoB) layer 320d, a boron-added gadolinium cobalt oxide (GdCoBO) layer 330d, and an iron cobalt boron (FeCoB) layer 340d Each layer is laminated in the order of a magnesium oxide (MgO) layer 350d. Note that the layer 320d and the layer 340d have the same boron content and the same thickness.

  A laminate 22c shown in FIG. 4C is a laminate including an example of the laminate 120 included in the above-described variable resistance element 22. Specifically, a portion including the layer 320c, the layer 330c, and the layer 340c included in the stacked body 22c corresponds to the stacked body 120 including the ferromagnetic material 210, the nonmagnetic material 220, and the ferromagnetic material 230. . On the other hand, each of the laminates shown in (a), (b), and (d) of FIG. 4A has a configuration similar to the laminate 120 included in the above-described resistance change element 22. For example, a portion including the layer 320a, the layer 330a, and the layer 340a included in the stacked body 22a illustrated in FIG. 4A (a), the layer 320b, the layer 330b included in the stacked body 22b illustrated in FIG. The portion composed of the layer 340b and the portion composed of the layer 320d, the layer 330d, and the layer 340d included in the laminated body 22d shown in FIG. 4D correspond to the laminated body 120 in terms of the substance contained in each layer. ing.

  FIG. 4B is an example of a graph in which the value of the magnetization amount indicated by a portion corresponding to the stacked body 120 in each of the stacked bodies measured when an external magnetic field is applied to each of the stacked bodies illustrated in FIG. 4A is plotted. Is shown. In the graph shown in FIG. 4B, the value of the amount of magnetization when a magnetic field is applied in a direction perpendicular to the interface between the layers of each laminate is plotted by a solid line. The value of the amount of magnetization when a magnetic field is applied in a parallel direction is plotted by a broken line.

  Specifically, in the graph of (a1) of FIG. 4B, the value of the magnetization amount indicated by the portion including the layer 320a, the layer 330a, and the layer 340a in the stacked body 22a is plotted. Similarly, in the graph of (b1) of FIG. 4B, the value of the amount of magnetization indicated by the portion including the layer 320b, the layer 330b, and the layer 340b in the stacked body 22b is plotted, and the graph of (c1) of FIG. In FIG. 4B, the value of the magnetization amount indicated by the portion including the layer 320c, the layer 330c, and the layer 340c in the stacked body 22c is plotted. In the graph of (d1) of FIG. The value of the magnetization amount indicated by the portion including 330d and the layer 340d is plotted.

  Further, in the graph of (a2) of FIG. 4B, the value of the amount of magnetization indicated by the portion including the layer 320a, the layer 330a, and the layer 340a when the thickness of the layer 330a is reduced in the stacked body 22a is plotted. . In the graph of (b2) of FIG. 4B, the value of the amount of magnetization indicated by the layer 320b, the layer 330b, and the layer 340b when the thickness of the layer 330b is reduced in the stacked body 22b is plotted.

  In all the graphs shown in FIG. 4B, the amount of magnetization when an external magnetic field having a magnitude of zero or near zero is larger in the direction perpendicular to the layer interface than in the direction parallel to the layer interface, and is shown in FIG. 4A. It can be seen that a portion corresponding to the laminate 120 among the respective laminates has perpendicular magnetic anisotropy. This indicates that the stacked body 120 also has perpendicular magnetic anisotropy.

[Operation example]
Next, a write operation of the storage device according to the first embodiment will be described.

  In the following description, the memory cell MC to be written is referred to as “selected memory cell MC”. The bit line BL, source line / BL, and word line WL corresponding to the selected memory cell MC are referred to as "selected bit line BL", "selected source line / BL", and "selected word line WL", respectively. On the other hand, the bit line BL, source line / BL, and word line WL that do not correspond to the selected memory cell MC are referred to as “unselected bit line BL”, “unselected source line / BL”, and unselected word line WL, respectively. Name.

  An “H” level voltage that turns on the selection transistor 21 included in the selected memory cell MC is applied to the selected word line WL. On the other hand, an unselected word line WL is supplied with an “L” level voltage that turns off the selection transistor 21 included in the corresponding memory cell MC. By performing such control and providing a potential difference between the selected bit line BL and the selected source line / BL, a write current is caused to flow through the resistance change element 22 included in the selected memory cell MC, and FIG. According to the spin injection writing method described above, the resistance change element 22 can be set to the low resistance state or the high resistance state.

  FIG. 5 is a schematic diagram illustrating an example of a write operation in which a write current is applied to the variable resistance element 22 to set the variable resistance element 22 from a low resistance state to a high resistance state in the storage device 1 according to the first embodiment. It is.

  First, in the state St1, the magnetization directions of the ferromagnetic materials 210 and 230 are parallel to the magnetization direction of the ferromagnetic material 140. At this time, the resistance change element 22 is in the low resistance state described with reference to FIG.

  Next, in the state St2, the electrons e derived from the write current flow from the ferromagnetic body 210 of the resistance change element 22 toward the ferromagnetic body 140. Many of the electrons e flowing from the ferromagnetic material 210 toward the ferromagnetic material 140 have spins in the same direction as the magnetization directions of the ferromagnetic materials 210 and 230, and such electrons e Simply pass through. On the other hand, a small number of electrons e flowing from the ferromagnetic material 210 toward the ferromagnetic material 140 have spins in the direction opposite to the magnetization direction of the ferromagnetic materials 210 and 230. By such electrons e, spin torque having a magnetization direction antiparallel to the magnetization direction of the ferromagnetic material 140 is injected into the ferromagnetic materials 210 and 230. The magnetization direction of the ferromagnetic materials 210 and 230 is affected by the injection of the spin torque. At this time, of the ferromagnetic materials 210 and 230, the magnetization direction of the ferromagnetic material 210 first starts to be reversed in a direction antiparallel to the magnetization direction of the ferromagnetic material 140. The perpendicular magnetic anisotropic magnetic field of the ferromagnetic material 210 is larger than the perpendicular magnetic anisotropic magnetic field of the ferromagnetic material 230, or the magnetic resonance magnetic field of the ferromagnetic material 210 is larger than the magnetic resonance magnetic field of the ferromagnetic material 230. This is because the frequency of the precession of the spin increases and the rotation speed increases because the magnetization damping constant of the ferromagnetic material 210 is larger than the magnetization damping constant of the ferromagnetic material 230. Further, the magnetization direction of the ferromagnetic material 230 located closer to the ferromagnetic material 140 among the ferromagnetic materials 210 and 230 is unlikely to be reversed by the leakage magnetic field from the ferromagnetic material 140.

  In the state St3, the reversal of the magnetization direction of the ferromagnetic material 210 is completed, but the write current continues to flow through the resistance change element 22 thereafter.

  Next, in the state St4, the electrons e spin-polarized by the ferromagnetic material 210 and the like flow into the ferromagnetic material 230. The spin-polarized electron e performs exchange interaction with the electron of the ferromagnetic material 230. As a result, a spin torque of the spin-polarized electron e and the electron of the ferromagnetic material 230 is generated. Many of the electrons e flowing into the ferromagnetic material 230 have spins in the same direction as the magnetization direction of the ferromagnetic material 210. Further, a small number of the electrons e flowing from the ferromagnetic material 230 toward the ferromagnetic material 140 have spins in the direction opposite to the magnetization direction of the ferromagnetic material 230. With such electrons e, spin torque having a magnetization direction antiparallel to the magnetization direction of the ferromagnetic body 140 is injected into the ferromagnetic body 230. Therefore, due to the spin torque, the magnetization direction of the ferromagnetic material 230 also starts to reverse in a direction antiparallel to the magnetization direction of the ferromagnetic material 140. Thus, STT occurs between the ferromagnetic material 210 and the ferromagnetic material 230.

  By continuing to supply the write current, in the state St5, the reversal of the magnetization direction of the ferromagnetic material 230 is also completed. At this time, the magnetization directions of the ferromagnetic materials 210 and 230 are antiparallel to the magnetization direction of the ferromagnetic material 140. That is, the resistance change element 22 is set to the high resistance state described with reference to FIG.

  FIG. 6 is a schematic diagram illustrating an example of a write operation in which a write current is applied to the variable resistance element 22 to set the variable resistance element 22 from a high resistance state to a low resistance state in the storage device 1 according to the first embodiment. It is.

  First, in the state St6, the magnetization directions of the ferromagnetic materials 210 and 230 are antiparallel to the magnetization direction of the ferromagnetic material 140. At this time, the resistance change element 22 is in the high resistance state described with reference to FIG.

  Next, in the state St7, the electrons e derived from the write current flow in the direction from the ferromagnetic body 140 to the ferromagnetic body 210 of the resistance change element 22. Many of the electrons e flowing into the ferromagnetic material 230 are spin-polarized by the ferromagnetic material 140 and have a spin in the same direction as the magnetization direction of the ferromagnetic material 140. The spin-polarized electron e performs exchange interaction with the electron of the ferromagnetic material 230. As a result, a spin torque of the spin-polarized electron e and the electron of the ferromagnetic material 230 is generated. Due to this spin torque, the magnetization direction of the ferromagnetic material 230 starts to be reversed in a direction parallel to the magnetization direction of the ferromagnetic material 140.

  In the state St8, the reversal of the magnetization direction of the ferromagnetic material 230 is completed, but the write current continues to flow through the resistance change element 22 thereafter.

  Next, in the state St9, the electrons e spin-polarized by the ferromagnetic material 230 and the like flow into the ferromagnetic material 210. The spin-polarized electron e performs exchange interaction with the electron of the ferromagnetic material 210. As a result, a spin torque of the spin-polarized electron e and the electron of the ferromagnetic material 210 is generated. Many of the electrons e flowing into the ferromagnetic material 210 have spins in the same direction as the magnetization direction of the ferromagnetic material 230. Therefore, due to the spin torque, the magnetization direction of the ferromagnetic material 210 also starts to reverse in a direction parallel to the magnetization direction of the ferromagnetic material 140. As described above, also when the resistance change element 22 is set to the high resistance state, the STT occurs between the ferromagnetic material 210 and the ferromagnetic material 230.

  By continuing to supply the write current, in the state St10, the reversal of the magnetization direction of the ferromagnetic material 210 is also completed. At this time, the magnetization directions of the ferromagnetic materials 210 and 230 are parallel to the magnetization direction of the ferromagnetic material 140. That is, the resistance change element 22 is set to the low resistance state described with reference to FIG.

  Since the nonmagnetic material 220 containing a boron-added rare earth oxide is a dielectric, for example, the nonmagnetic material 220 is generally a voltage-controlled magnetic material that changes magnetic characteristics by an electric field generated at the interface between the insulator and the magnetic material. An anisotropic (VCMA: Voltage-Controlled Magnetic Anisotropy) effect can be exhibited. In the example of the write operation described with reference to FIGS. 5 and 6, the VCMA effect by the non-magnetic body 220 may be used. For example, in the reversal of the magnetization direction of the ferromagnetic body 210 in the state St2 and the reversal of the magnetization direction of the ferromagnetic body 230 in the state St7, the energy barrier of the reversal of the magnetization direction may be reduced by using the VCMA effect. It is possible.

[effect]
When a structure including two ferromagnetic materials is used as the storage layer, the reversal of the magnetization directions of the two ferromagnetic materials can be efficiently performed by using the STT between the two ferromagnetic materials. As a result, the writing current of the storage layer can be reduced. It is conceivable to use MgO between ferromagnetic materials for the purpose of using STT. FIG. 7A shows such an example, and is a cross-sectional view of an exemplary laminate 32 as a comparative example of the first embodiment.

  In the laminate 32, a boron-added gadolinium oxide (GdBO) layer 410, an iron cobalt boron (FeCoB) layer 420, a magnesium oxide (MgO) layer 430, an iron cobalt boron (FeCoB) layer 440, and a magnesium oxide (MgO) layer 450 Each layer is laminated in this order. Note that the stacked body 32 includes a magnesium oxide (MgO) layer 430 instead of the boron-added gadolinium oxide (GdBO) layer 330b as compared with the stacked body 22b shown in FIG. 4B. Except for this, each of the other layers has the same constituent material and thickness.

  FIG. 7B plots the value of the amount of magnetization indicated by the portion including the layer 420, the layer 430, and the layer 440 of the stack 32 measured when an external magnetic field is applied to the stack 32 illustrated in FIG. 7A. 4 shows an example of a graph. In the graph shown in FIG. 7B, the value of the amount of magnetization when a magnetic field is applied in a direction perpendicular to the interface of the layers of the stacked body 32 is plotted by a solid line. The value of the amount of magnetization when a magnetic field is applied in a parallel direction is plotted by a broken line.

  Specifically, in the graph of (a) of FIG. 7B, the value of the amount of magnetization indicated by the portion including the layer 420, the layer 430, and the layer 440 in the stacked body 32 is plotted. In the graph of FIG. 7B, when the thickness of the layer 430 is reduced, the value of the magnetization amount indicated by the portion including the layer 420, the layer 430, and the layer 440 is plotted.

  In any of the graphs shown in FIG. 7B, the amount of magnetization when an external magnetic field having a magnitude of zero or near zero is applied is larger in the direction parallel to the layer interface than in the direction perpendicular thereto. It can be seen that, of the laminated body 32 shown, the iron cobalt boron (FeCoB) layers 420 and 440, which are ferromagnetic substances, do not have perpendicular magnetic anisotropy. Therefore, when MgO is used between the ferromagnetic materials of the storage layer including a plurality of ferromagnetic materials, such a structure cannot be used as a storage layer having perpendicular magnetization.

  On the other hand, in the storage device 1 according to the first embodiment, the stacked body 120 functioning as a storage layer includes the ferromagnetic material 210, the non-magnetic material 220 including the boron-doped rare earth oxide, and the ferromagnetic material 230. Including. In such a laminate 120, the ferromagnetic materials 210 and 230 have perpendicular magnetic anisotropy. Therefore, a storage layer having perpendicular magnetization can be realized.

  The higher perpendicular magnetic anisotropy is obtained when the boron-added rare earth oxide is used as compared with the case where MgO is used as the non-magnetic material 220, because the rare earth oxide has a higher boron absorption capacity. After depositing the laminated film of FIG. 3, for example, when heat treatment is performed, boron in the ferromagnetic material 210 and the ferromagnetic material 230 is absorbed in the non-magnetic material 220, and the non-magnetic material 220 is It becomes a boron-added rare earth oxide having a boron concentration higher than 230. The non-magnetic material 220 becomes amorphous due to boron accumulated in the non-magnetic material 220, and the ferromagnetic material 210 and the ferromagnetic material 230 become crystallized. As a result, when the boron-added rare earth oxide is used for the nonmagnetic material 220, the residual boron of the ferromagnetic material 210 and the ferromagnetic material 230 is smaller than when MgO is used as the nonmagnetic material 220, and the strain is reduced. Then, crystallization is further promoted, so that a high perpendicular magnetic anisotropic magnetic field can be obtained.

  Further, according to the storage device 1 according to the first embodiment, the reversal of the magnetization of the stacked body 120 can be realized using a relatively low write current, as described below.

  Generally, in reversing the magnetization direction of a ferromagnetic material, it is necessary to apply a write current having a magnitude exceeding the energy corresponding to the thermal disturbance resistance of the ferromagnetic material. On the other hand, the perpendicular magnetic anisotropic magnetic field (Hk), the magnetic resonance magnetic field (Hr), and / or the magnetization damping constant (α), and / or the magnetization amount (Mst) of the ferromagnetic materials 210 and 230 are Have the magnitude relationship as described above. As a result, as described with reference to FIGS. 5 and 6, the reversal of the magnetization direction of each of the ferromagnetic materials 210 and 230 can be started independently in order. Therefore, as described with reference to FIGS. 5 and 6, by inverting the magnetization of the ferromagnetic materials 210 and 230 using the STT between the ferromagnetic materials 210 and 230, the magnetization direction of the stacked body 120 is changed. Can be inverted. Therefore, the write current in the first embodiment is the same when the ferromagnetic materials 210 and 230 have the same perpendicular magnetic anisotropy magnetic field, magnetization resonance magnetic field, and / or magnetization damping constant, and / or magnetization amount. It is lower than the write current in some cases.

  Furthermore, by using the VCMA effect of the nonmagnetic material 220 containing, for example, a boron-added rare earth oxide, the energy barrier for reversing the magnetization direction of the stacked body 120 can be further reduced.

[Modification]
In the first embodiment, the reduction of the energy barrier for reversing the magnetization direction of the stacked body 120 using the VCMA effect of the nonmagnetic body 220 containing, for example, a boron-added rare earth oxide has been described. For example, the following method may be used as a method for reducing the energy barrier by using a voltage drop similarly to the VCMA effect.

  For example, the ferromagnetic material 210 may be configured to include iridium (Ir). Further, the ferromagnetic material 230 may be configured to include platinum (Pt). As a result, a voltage drop is realized similarly to the VCMA effect, and therefore, the energy barrier for reversing the magnetization direction of the stacked body 120 can be further reduced.

<Other embodiments>
In this specification, the term “connection” indicates that the elements are electrically connected, and does not exclude the case where another element is interposed therebetween.

  The variable resistance element described in the above-described first embodiment and the modified example is, for example, a case in which a laminate functioning as a storage layer is a bottom-free type provided below a ferromagnetic material functioning as a reference layer, for example. But is not limited to this. For example, the resistance change element may be of a top-free type in which, for example, a laminate functioning as a storage layer is provided above a ferromagnetic material functioning as a reference layer, for example.

  Further, in the above-described first embodiment and the modifications, the magnetic storage device including the MTJ element has been described as an example of the storage device including the variable resistance element. However, the devices according to these embodiments and the like are not limited thereto. For example, the devices according to these embodiments and the like include other devices that require a magnetic element having perpendicular magnetic anisotropy, such as sensors and media. The magnetic element is an element including at least a stacked body including two ferromagnetic materials and a nonmagnetic material provided between the two ferromagnetic materials functioning as, for example, a storage layer, as described with reference to FIG. Further, for example, the non-magnetic material described as functioning as the underlayer may have conductivity, and is not limited to a non-magnetic material and may be a ferromagnetic material.

  Furthermore, in the write operation described in the above-described first embodiment, the operation of controlling the write current to perform writing to the variable resistance element has been described, but the present invention is not limited to this. For example, in the write operation, control of the write current and control of the write voltage may be used in combination.

In the above embodiment, a configuration using a three-terminal selection transistor as the switching element has been described, but the switching element may be, for example, a two-terminal switch element.
When the voltage applied between the two terminals is equal to or less than the threshold, the switch element is in a “high resistance” state, for example, is electrically non-conductive. When the voltage applied between the two terminals is equal to or higher than the threshold, the switch element changes to a “low resistance” state, for example, an electrically conductive state.

  The switch element may have this function regardless of the polarity of the voltage. That is, the two-terminal switch element may have the above-described function in both directions.

  The switch element may include, for example, at least one or more chalcogen elements selected from the group consisting of Te, Se, and S. Alternatively, chalcogenide, which is a compound containing the chalcogen element, may be included. The switch element may further include at least one element selected from the group consisting of B, Al, Ga, In, C, Si, Ge, Sn, As, P, and Sb.

  Such a switch between two terminals is connected to a magnetoresistive element via two contact plugs as in the above-described embodiment. Of the two contact plugs, the contact plug on the magnetoresistive element side contains, for example, copper. A conductive layer (for example, a layer containing tantalum) may be provided between the magnetoresistive element and the contact plug containing copper.

  Although several embodiments have been described above, these embodiments have been presented by way of example only, and are not intended to limit the scope of the invention. These novel embodiments can be implemented in other various forms, and various omissions, replacements, and changes can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and are also included in the invention described in the claims and their equivalents.

  DESCRIPTION OF SYMBOLS 1 ... Storage device, 11 ... Memory cell array, 12 ... Current sink, 13 ... Sense amplifier and write driver, 14 ... Row decoder, 15 ... Page buffer, 16 ... Input / output circuit, 17 ... Control part, 20 ... Semiconductor substrate, 21 ... Select transistor, 22. Resistance change element, 23, 28, 30. Wiring layer, 24. Source or drain region, 25. Insulating layer, 26, 27, 29 .. Contact plug, 31 .. Interlayer insulating film, 110, 130 , 220: non-magnetic material, 120: laminated body, 140, 210, 230 ... ferromagnetic material, 310a, 350a, 350b, 350c, 310d, 350d, 430, 450 ... magnesium oxide (MgO) layer, 320a, 340a, 320b , 340b, 320c, 340c, 320d, 340d, 420, 440... (FeCoB) layer, 330a, 310b, 330b, 330c, 410: boron-added gadolinium oxide (GdBO) layer, 310c: hafnium boron (HfB) layer, 330d: boron-added gadolinium cobalt oxide (GdCoBO) layer, SA: Sense amplifier, WD: Write driver, MC: Memory cell, BL: Bit line, / BL: Source line, WL: Word line

Claims (10)

Equipped with a variable resistance element,
The variable resistance element includes a first ferromagnetic material, a second ferromagnetic material, and a first non-magnetic material including a boron-added rare earth oxide provided between the first ferromagnetic material and the second ferromagnetic material. A laminate including a magnetic material,
Storage device.   2. The storage device according to claim 1, wherein the first ferromagnetic material, the first non-magnetic material, and the second ferromagnetic material form a magnetic tunnel junction. The variable resistance element includes a third ferromagnetic material, and a second non-magnetic material provided between the stacked body and the third ferromagnetic material,
The second nonmagnetic material is on the opposite side of the second ferromagnetic material from the first nonmagnetic material,
3. The storage device according to claim 2, wherein a perpendicular magnetic anisotropic magnetic field (Hk) of the first ferromagnetic material is larger than a perpendicular magnetic anisotropic magnetic field of the second ferromagnetic material. The variable resistance element includes a third ferromagnetic material, and a second non-magnetic material provided between the stacked body and the third ferromagnetic material,
The second nonmagnetic material is on the opposite side of the second ferromagnetic material from the first nonmagnetic material,
The storage device according to claim 2, wherein a resonance magnetic field (Hr) of the magnetization of the first ferromagnetic material is larger than a resonance magnetic field of the magnetization of the second ferromagnetic material. The variable resistance element includes a third ferromagnetic material, and a second non-magnetic material provided between the stacked body and the third ferromagnetic material,
The second nonmagnetic material is on the opposite side of the second ferromagnetic material from the first nonmagnetic material,
The storage device according to claim 2, wherein a damping constant (α) of the first ferromagnetic material is larger than a damping constant of the second ferromagnetic material. The variable resistance element includes a third ferromagnetic material, and a second non-magnetic material provided between the stacked body and the third ferromagnetic material,
The second nonmagnetic material is on the opposite side of the second ferromagnetic material from the first nonmagnetic material,
The storage device according to claim 2, wherein a magnetization amount (Mst) of the first ferromagnetic material is smaller than a magnetization amount of the second ferromagnetic material.   The storage device according to claim 6, wherein a saturation magnetization (Ms) of the first ferromagnetic material is smaller than a saturation magnetization of the second ferromagnetic material. The variable resistance element includes a third ferromagnetic material, and a second non-magnetic material provided between the stacked body and the third ferromagnetic material,
The second nonmagnetic material is on the opposite side of the second ferromagnetic material from the first nonmagnetic material,
The storage device according to claim 2, wherein at least the first ferromagnetic material includes iridium (Ir), or the second ferromagnetic material includes platinum (Pt).   The first non-magnetic material includes scandium (Sc), yttrium (Y), lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium ( Eu), at least one of gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu) The storage device according to claim 1.   The storage device according to claim 1, further comprising a memory cell including the variable resistance element.